1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of fabricating the same, and more particularly, to a liquid crystal display device having a high aperture ratio and a method of fabricating the same.
2. Discussion of the Related Art
Many efforts are being made to study and develop liquid crystal display (LCD) devices because of their high resolution images, light weight, small thickness, compact size, low power supply requirements, and lesser power consumption.
In general, a LCD device uses an optical anisotropy of liquid crystal materials, and controls light transmissivity through the device by applying an electric field, thereby varying an arrangement of liquid crystal molecules within a liquid crystal material layer to produce an image. A LCD device generally includes upper and lower substrates, which are spaced apart and face each other, and a liquid crystal material layer interposed between the upper and lower substrates. Each of the substrates includes an electrode, where the electrodes face each other. In addition, the LCD device includes thin film transistors and pixel electrodes arranged in a matrix and such a LCD device is generally referred to as an active matrix liquid crystal display (AMLCD) device.
FIG. 1 is a cross-sectional view of a liquid crystal display device according to the related art. In FIG. 1, a LCD device 10 includes first and second substrates 12 and 14 facing each other with a predetermined space therebetween. A liquid crystal material layer 16 is interposed between the first and second substrates 12 and 14. The LCD device 10 has an image area A and a non-image area B surrounding the image area A, where images are displayed within the image area A.
In the image area A, a gate electrode 18 is formed on an inner surface of the first substrate 12. A gate insulating layer 20 is formed on the gate electrode 18, and the gate insulating layer 20 extends to the non-image area B. An active layer 22 is formed on the gate insulating layer 20 and is disposed over the gate electrode 18. In addition, a data line 25 and source and drain electrodes 24 and 26 are formed on the active layer 22. The gate electrode 18, the active layer 22, and the source and drain electrodes 24 and 26 form a thin film transistor T. A data pad 27 is formed on the gate insulating layer 20 in the non-image area B to connect the data line 25 to outer circuits (not shown).
Furthermore, a passivation layer 28 is formed on the data line 25, the source and drain electrodes 24 and 26, and the data pad 27. The passivation layer 28 has a drain contact hole 29 and a data pad contact hole 30 exposing the drain electrode 26 and the data pad 27, respectively. Moreover, a pixel electrode 32 and a data pad terminal 33 are formed on the passivation layer 28. The pixel electrode 32 is located in a pixel region P of the image area A and connected to the drain electrode 26 through the drain contact hole 29. The data pad terminal 33 is situated in the non-image area B and is connected to the data pad 27 through the data pad contact hole 30.
In addition, a black matrix 34 is formed on an inner surface of the second substrate 14, which is smaller than the first substrate 12. The black matrix 34 corresponds to the thin film transistor T in the image area A, and is disposed in the non-image area B. Furthermore, a color filter layer 36 is formed on the black matrix 34, and has three sub-filters of red (R), green (G), and blue (B) disposed in the pixel region P. An overcoat layer 38 is formed on the color filter layer 36, and a common electrode 40 is formed on the overcoat layer 38.
Moreover, first and second alignment layers (not shown) are formed on the pixel electrode 32 and the common electrode 40, respectively, to arrange liquid crystal molecules of the liquid crystal material layer 16. Then, a spacer 42 is formed in the liquid crystal material layer 16 to maintain a uniform cell gap forming a uniform thickness of the liquid crystal material layer 16.
A seal pattern 44 is formed in the non-image area B between the first and second substrates 12 and 14 to prevent the liquid crystal material of the liquid crystal material layer 16 from leaking. In addition, first and second polarizers 31 and 35 are arranged over outer surfaces of the first and second substrates 12 and 14, respectively. Further, a back light unit (not shown) is located over the first polarizer 31 as a light source. Accordingly, the black matrix 34 covers the seal pattern 44, such that the black matrix 34 blocks light L1 around the seal pattern 44 from the back light unit, and prevents light leakage in the non-image area B. However, the black matrix 34 decreases an aperture ratio of the LCD device, thereby reducing the image area A. Moreover, since the black matrix 34 should have a margin in order to prevent misalign of the first and second substrates 12 and 14, thereby increasing the non-image area B.
Recently, a high aperture ratio LCD device has been proposed. In the high aperture ratio LCD device, gate and data lines are used as a black matrix by forming a passivation layer with a low dielectric material and overlapping a pixel electrode with the gate and data lines.
In addition, a LCD device having a thin film transistor on color filter (TOC) or color filter on thin film transistor (COT) structure, which includes a color filter layer and a thin film transistor on one substrate, has also been proposed. In the LCD device having the TOC or COT structure, a black matrix is formed on the substrate that includes the color filter layer and the thin film transistor, such that the black matrix corresponds to the thin film transistor and does not require a black matrix margin.
However, in the aforementioned high aperture ratio LCD device and the LCD device having the TOC or COT structure, the black matrix does not cover a seal pattern in the non-image area. Thus, in these LCD devices, light leakage occurs in the non-image area, thereby reducing light usage efficiency of the devices.